Condensation in loft - problem with builder?? HELP

[vj32]

We have a condensation problem in our loft which 3 different builders have said is because the loft hatch isn't insulated.

The loft hatch is new, put in in September. The previous one it replaced was smaller but insulated well. The guy who installed the new loft ladder and hatch says you can't insulate a hinged drop down loft hatch, and that an uninsulated loft hatch (its just a piece of soft wood!) will not cause condensation.

Having had it explained by three builders as the cause... I believe them rather than the original guy who did the loft as it seems common sense as its a big area left uninsulated.

I complained to the guy but he was very defensive on the phone. Anyone know anything about this or got any advice? He is coming back to put a seal on the loft hatch but I don't think this is enough.

condensation in a loft is caused by warm moist air getting in, and not getting out.

Lack of insulation will not be the cause.

If the loft hatch is a loose fit, it will enable more warm moist air from the house to rise up (water vapour is lighter than air, so it rises through the house until it either escapes, or finds something to condense on.

If you drape wet washing around your house, this will be a terrible source of water vapour and condensation. The other big cause is ceilings with holes in them, for example for pipes or downlighters, especially if they are in a bathroom.

As well as dealing with water-vapour ingress, you can improve the ventilation of your loft to let the water vapour escape. Have a look at the loft insulation. If it is pushed right into the eaves, roll it back a bit and tuck the end under so there is a few inches gap and you can see daylight. It only needs to cover the plaster ceiling.

It is also possible to ventilate the seams in the roofing felt (I am assuming that you can't see the underside of your tiles or slates) or even to put a vent in the gable wall. Lofts should be cold and draughty.

Sorry Pigletjohn, didn't give quite the full story.

We have no vents in the loft, at all. We have checked this. So I am getting roof vents installed, getting a bathroom extractor put in and have already bought a big electric dehumidifier. But all 3 builders who came to look at doing the roof vents mentioned the lack of insulation on the roof hatch as being a problem (its probably double the size of a normal one as it had to be extended), and actually the roof hatch itself is now showing black mould. So I'm worried we are going to have spent £1k and not solved the problem. We don't really have the money to do any of this but our house is rotting so got to do something...

you could put a slab of Celotex on it if you want (it has twice the insulating power as the same thickness of mineral wool) and it will cut heat loss, but it's not the cause of the condensation.

Do you drape wet washing in the house?

A bit, as I use cloth nappies, so maybe three loads of washing a week of things that can't be tumbled. But they are in the room with the dehumidifier so can't be doing that much damage surely?

Its just all very worrying as no-one seems to have a definitive 'right' answer about what to do or what exactly the problem is other than the lack of roof vents. But that didn't cause a problem last winter.

Thanks for your time.

assuming you are south of Scotland, there was almost no frost last winter or the one before.

there are a lot of people who suddenly have very damp lofts. This is because it has been cold enough for the water vapour to freeze on the underside of the roof, and then when the temperature goes up again it melts and makes big drips.

most of those with the problem are those who got free extra loft insulation in the last couple of years, i.e the elderly. It is happening big time in a house known to me - one with a lot of downlighters and many long hot baths and showers...

the residents are looking to implement exactly what PJ suggests, if they can find someone reliable to sort out the 'chuck it down and run away' approach of whoever put the extra insulation in.

We developed terrible condensation in our loft, a few years ago - not quite sure why even now. Possibly due to increased insulation over the whole house and / or having a wall built between the loft space in our neighbours' house (they also developed problems). It was bad enough that there was actually water damage to some of the ceilings.

Anyway, we had roof vents fitted which totally fixed the problem. Incidentally, we found that rolling back the insulation round the eaves resulted in mouldy patches on the ceiling.

Anyway, we had roof vents

Random repetition there

I agree with a lot about the causes and I'm trying to sort them out. Thanks everyone.

The main thing though, is it usual to have a non-insulated loft hatch or is that normal? It seems weird to insulate the loft with a foot of insulation and then it be OK to have more than a metre sq with just a sheet of wood and no insulation at all. (Previous owner of house was a pensioner so loft has very thick insulation done under a grant.)

Older yellow fibreglass or mineral wood sheds dust and fibres (I only use the stuff treated with Ecose now, which is brown and non-shedding). Some people find it irritant.

So having it on the hatch is likely to have fibres fall into the house when you open it, and they were often left bare.

Modern loft hatches are prefabricated with a layer of insulating foam.

I would try fixing a slab of Celotex or Kingspan rigid foam to the upper surface of the hatch. If it likely to be rubbed or scratched, a piece of thin ply will help protect it. It would be extra work to fabricate something if you have a loft ladder.